Over the recent years, computer hardware has become progressively smaller. Current hand-held computerized and communications devices are small so that they can be comfortably held in one's pocket. Most widely-used small-sized devices, such as personal data assistants (PDAs), smart phones, Tablet PC's, wrist watches, car navigating systems and the like are today routinely provided with communications and computing capabilities. One drawback of size miniaturization is the failure to provide efficient text input means. The specific device limiting further miniaturization and enhanced utilization of handheld devices is the keyboard. Since the keyboard is the main input unit used by practically all computing devices the size limitation enforced on the keyboard by the small size of the host device is a serious drawback. Furthermore, the limited size of the keyboards on small-sized devices makes finger-based or thumb-based input problematic. In order to alleviate the problem various artificial input devices, such as a stylus or a pen, are typically used making the input process physically awkward, unnatural error-prone, and considerably slower than finger-based input.
Alternative input technologies, such as voice interfaces are being continuously developed, but such techniques are still inaccurate, do not provide privacy in public places and work with difficulties in noisy environments. The text input systems available today on handheld devices prevent the full use of keyboard applications such as mobile e-mail and mobile word-processing. As a result, at present, mobile communication is limited to voice applications and substantially limited text input systems, such as SMS.
U.S. Pat. No. 6,801,190 entitled “Keyboard system with automatic correction” describes a mini-QWERTY keyboard. The keyboard is designed to correct inaccuracies in keyboard entries. This patent is mainly directed towards single-point entries. The engine metric is well known and is based on the sum of the distances between the contact points and the known coordinates of a character or a plurality of characters on the keyboard. Although the patent mentions incidentally the possible use of a finger in order to input data, the keyboard system layout and engine are clearly not adapted to finger input. The input resulting from a thumb can be easily too scattered to belong only to the “auto-correcting keyboard area” (the part of the keyboard containing the letters). It may then touch other keyboard regions such as the space key or any other function or punctuation, leading to fatal misinterpretations. In fact, a letter interpreted as a disambiguation key (such as the space key) will lead to a premature disambiguation and therefore will leave almost no chance for a correct disambiguating process to happen. Likewise, a disambiguation key interpreted as a letter will lead to the same problem. In contrast to this reference, the present invention is based on a finger input represented by a cluster of points or a surface. In addition, the keyboard layout of the present invention is designed to prevent ambiguities between the letters region and the remaining parts of the keyboard. Finally, the system metric is based on density distribution instead of distance between points.
Keyboards using multiple-letter keys and equipped with a disambiguation system are not new. The system called T9 and based on U.S. Pat. No. 6,307,548, is well known and it is included in almost all cellular phones today. The keyboard is composed of 8 keys containing a plurality of letters. Each letter is input by a single keystroke. A disambiguation process provides the most likely output. The above patent quotes many other patents dealing with reduced keyboards. This patent and all the above patents, refer to keyboard systems with a fixed number of predefined characters per key. None of them disclose dynamic keys. Instead of considering keys, the present invention works with keyboard regions. The plurality of letters for each keystroke depends on the magnitude of the input area and the letters that may be associated together in a given keystroke vary. The difference between these inventions and the present one is crucial since, in the present invention, the user activates a region surrounding a character instead of aiming at a single small key.
U.S. Pat. No. 5,952,942 refers to a “Method and device for input of text messages from a keypad”. This method refers to the use of a classical phone keypad in which each key represents up to 4 characters. A new object is created each time a keystroke representing a set of candidate characters is added to a previous object (“old object”). The previous object may contain several candidates that are words or beginnings of words (word-stems). At the stage of the formation of the new object, a matching process is activated. All the possible combinations of letters resulting from the addition of the last keystroke to one of the old object candidates are matched with the dictionary in order to check the existence of a word or the beginning of a word belonging to the dictionary. As seen, this process is repeated for each keystroke. To each new object, the non-rejected sequences are the ones that are words or can lead to future words (word-stems). The elimination is therefore sequential. In contrast to this reference, in the present invention, disambiguation is preferably executed only when the word is terminated. Furthermore, in the present invention, a parameter measuring the input accuracy is used in conjunction with the frequency of use in order to sort the solutions. In the present invention, the above parameter is obtained by summing relevant input densities.
U.S. Pat. No. 6,307,548 refers to a “Reduced keyboard disambiguating system”. The principle of this keyboard relies on the fact that it is made of ambiguous keys, wherein each key contains a few letters or symbols. The patent describes a disambiguating process in which the system is equipped with a database (“dictionary”) of 24,500 words organized in a tree structure. Each word belongs to a given node in the pre-determined tree structure of the dictionary and can be accessed only through its parent node. In that system, each word is represented by a unique combination of keystrokes and each keystroke combination can correspond to a few words. Consequently, there is only one way to tap a given word, and when it is not input accurately, it cannot be correctly identified by the system The disambiguation engine can be represented by a one-to-many function. The structure of the dictionary is determined in advance. Each time a character is input, the search tree eliminates the combinations, which are not words or part of words (word-stem). This algorithm is not workable when the number of characters per key is dynamic since the structure of the dictionary is pre-determined.
U.S. Pat. No. 6,556,841 refers to a spelling corrector system. This patent employs the use of a classical phone keypad, in which each key corresponds to 3 or 4 letters. The selection of one of the letters belonging to a key is reached by tapping one or several times the corresponding key (each tap leads to the display of a subsequent letter of the key). The purpose of this patent is to take into account the possibility that the user may have, while inputting a word, tapped a key with an inaccurate number of occurrences, leading to an incorrect selection of the letter. The method used in this patent is to check whether the user has written words belonging to a given dictionary, and in case they do not, propose alternative solutions. These solutions must belong to the dictionary and have the same combination of keys (only the multiple tapping on a given key may be incorrect). The disambiguation process begins when a termination symbol is tapped at the end of a word. In case the word does not belong to the dictionary, it replaces successively each letter of the word with one of the letters belonging to the same key. Each word resulting from this transformation is matched with the dictionary. Alternatives belonging to the dictionary are proposed to the user. The algorithm employed is based on the combinatory of all the possible words created by a sequence of keystrokes. In contrast to this patent, in the present invention the disambiguation is preferably performed by elimination of all the words whose letters do not satisfy the sequence of keystrokes. The referenced invention does not correct an error on the keys location but only an error on the number of keystrokes on a given key. There is no possibility of using a matching parameter measuring the input accuracy in order to sort the candidates (in case of multiple solutions). By its very definition, the referenced invention refers to keypads or keyboards with a predefined number of characters per key and is therefore not adapted for dynamic disambiguation.
There is therefore a need for high-speed, natural and accurate text input systems having a compact keyboard area and automatic input disambiguating capabilities to be applicable for the known keyboard layouts. Such a text-input system will make easily available e-mail, instant messaging and word processing on Tablet PC's, PDAs, wrist watches, car dashboard systems, smart and cellular phones, and the like. In order to make such a keyboard popular, the keyboard will be of a miniature size to provide the option of fitting such a keyboard into handheld devices having the smallest dimensions. In addition, the layout has to be intuitively designed, such as for example, the QWERTY layout design, and the input has to be performed via the utilization of two thumbs or fingers In order to negate the need for using artificial input devices such as a stylus or a pen.